For one, it's realistic.

Also, not having to process snow and rain above absurd heights seems like it would be pretty beneficial.

Could link in very well with #143, which would control where rain and snow would start in the first place. Would probably have to be fixed per world though as to not allow for weird continuity errors with snow generation at high altitudes.

This is not how it works in vanilla. Also clouds are purely clientside construct. This would have to be serverside. Might be a configurable option, but definitely not the default